Can dogs sense pregnancy?

Our dog, Jimmy has always been my little follower. As soon as I get home, he usually greets me at the door and then shadows me everywhere. We have definitely seen some differences in Jimmy over the past few weeks/months, especially this weekend. I have been telling Zach that I think he senses there are changes ahead. Everytime I am sitting on the couch, he comes next to me and lays his head on my tummy. It's very apparent as to what is going on. He follows me everywhere, which is normal but he has been just standing and staring at me when I am just relaxing on the couch as well. He just can't relax and is constantly wanting attention from both Zach and I. I'm so excited to see how he will interact with Avery when she is here but worried that he will be jealous. He has always been really great around children...I suspect he will be her little protector. We will just have to make sure we show him the attention he needs once she arrives.